Method for producing gas exchange package

ABSTRACT

To provide a method of manufacturing a gas displacement package that can cope with packages with various sizes and shapes, and a sealing packaging container, and a package. A method of manufacturing a gas displacement package and a sealing packaging container, and a package, wherein a packaging container comprising a receptacle and a lid of plastic is used, ridges of the receptacle and the lid overlapped each other, the ridges are sealed with a band tape, and the container is gas displaced through a hole of the container and is sealed.

TECHNICAL FIELD

The present invention relates to method of manufacturing a gasdisplacement package and a sealing packaging container and the package.

BACKGROUND ART

Hitherto, it is general that individual households buy foodstuff andcook them to eat. Recently, however, for the intention of effectinghousework simply, life style is increased in which households buy foodproducts, which are previously cooked in a food processing room or acentral kitchen of a supermarket or the like, at supermarkets orconvenience stores to eat at home. In the cooked food field,developments of not only contents but also packages with various sizesor shapes have been greatly effected in order to provide best displaysby changing shapes and designs of the packages.

Especially, in a deli field, unlike a conventional sales manner in whichone kind of food product is sold in large quantity, food products cookedby many cooking methods are divided into small portions for morevariation and sold so that consumers can choose the products as desired.Thus, for clerks of delis at supermarkets or convenience stores, itbecomes a problem that cumbersome and complication required for changingdevices at the time of packaging various kinds of food products in smallquantity, reduction in production efficiency caused by the complicatedchanging, and complicated control of packaging machine parts forrespective packages for various kinds of food products in smallquantity.

On the other hand, it is in trend that cooked food products in whichoriginal flavors of ingredients are utilized are desired, but foodproducts with reduced food additives soon become rotten and have shortproduct cycles. This causes problems of need of many hands or reductionin a yield of food processing.

As a method of preserving products for a long period, gas displacementpackaging is known that preserves food products under an inert gasatmosphere to increase a distance of product distribution, reduceproducts that have fallen out of date, and increase productionefficiency. As an example of such gas displacement packaging,JP-A-9-295677 discloses a gas filling packaging method in which a gasfilling packaging tray is used that includes a tray on which a substanceis placed and a lid that covers the tray, the lid having a gas blow-ininlet on a top thereof and a gas outlet therearound, to cover the entiretray with a heat-shrinkable film having a gas barrier property. Thismethod allows gas to be blown in through the gas inlet and exhaustedthrough the outlet around the lid, thus allowing air remaining in thetray covered by the lid to be displaced by gas.

JP-A-4-189721 discloses a method in which there is provided aninsulating base plate having a heating element at an edge of a holeopened in a plate, a container is placed with a flange of the containerapplied to the heating element, and then filled with contents, subjectedto gas displacement in a vacuum chamber, and covered with a lid, andafter conveyed by a conveyer, a pressing plate is lowered from above thecontainer to perform heat bonding of the container and the lid with adie of a heated seal device.

Further, JP-A-61-103 discloses a method in which a container made of asynthetic resin sheet is filled with contents, an opening of thecontainer is covered with a sealing film or sheet, and then the entireopening of the container is thermally pressed from an upper surface ofthe sealing film or sheet by a heat roll to thermally bond a peripheryof the opening.

However, the method represented by JP-A-9-295677 is a method in whichthe gas is simply flushed into the package through the gas blow-in inletat the top of the lid, and the air is exhausted through the gas outlet,thus a rate of displacement when the gas displaces the air in a space inthe package is low, and depending on shapes of the contents, oxygencontained in the contents cannot be sometimes displaced by thedisplacement gas. The entire package is covered with the heat-shrinkablefilm having the gas barrier property, thus cutouts of the gas blow-ininlet at the top of the lid or the gas outlet tend to break the film tocause leakage of the filled gas. Besides, because of double packaging ofthe container and the film, the number of packaging materials are lot,causing a problem of increase in entrepreneur's bearing of cost based onthe Container and Package Recycling Law.

On the other hand, the gas displacement method disclosed inJP-A-4-189721 requires the heat element corresponding to each of variouscontainers with different sizes or designs. This requires a seal dieresistant to pressure that accommodates changes in atmospheric pressurein the chamber, and such a dedicated seal die for each container isexpensive to manufacture.

The method disclosed in JP-A-61-103 causes thermal deformation of thesealing film or sheet when the sealing film or sheet is thermallypressed on the opening of the container by the heat roll. When thecontent protrudes beyond the depth of the container, there are problemsthat the content is pressed by the top film, or the films overlap toeach other at flange of the container to make wrinkles and cause foreignmatters to be mixed into through clearances. In addition, like the abovedescribed example, this method has a problem that, for containers withdifferent shapes, heating dies corresponding to the shapes have to beprovided.

The present invention has an object to provide a method of manufacturinga gas displacement package and a sealing package that allows air in aspace and a content in the package to be displaced by gas at a high rateof displacement, complies with the Container and Package Recycling Law,and facilitates changes in shapes and sizes of the package.

DISCLOSURE OF THE INVENTION

A method of manufacturing a gas displacement package according to thepresent invention is characterized in that a container comprises areceptacle and a lid, the receptacle and the lid are overlapped eachother at respective edge portions to cover a top of the receptacle, theoverlapped portions are sealed with a band tape, the container has ahole, air in the container is expelled through the hole and displaced bygas other than air, and then the hole is sealingly closed.

It is preferable that the container is made of plastic.

It is preferable that the container, the band tape and an adhesive labelhave a gas barrier property.

It is preferable that the receptacle and the lid have at their edgeportions flanges including horizontal portions horizontally extendingfrom openings, substantial vertical portions vertically extending fromends of the horizontal portions, and ridges at boundaries between thehorizontal and vertical portions, and among the vertical portions of theflanges, the vertical portion located inside with respect to thecontainer is longer than the vertical portion located outside withrespect to the container, the inside vertical portion has a step at aportion in contact with an end of the outside vertical portion, and theband tape is adhered over the step for sealing.

It is preferable that the hole for gas displacement is provided on a topsurface of the lid.

It is preferable that the vertical portions of the flanges verticallyextend downwards from the horizontal portions.

A packaging container according to the present invention ischaracterized in that a receptacle and a lid have at their edge portionsflanges including horizontal portions horizontally extending fromopenings, and substantial vertical surfaces vertically extending fromends of the horizontal portions, and among the flanges, the verticalportion located inside with respect to the container is longer than thevertical portion located outside with respect to the container, and theinside vertical portion has a step at a portion in contact with an endof the outside vertical portion.

A ridge of the lid and/or the ridge of the receptacle may have recessesformed in such a manner that the vertical portion is dented inwardly andthe horizontal portion is dented downwardly.

The packaging container may have a reinforcing surface that extendsoutwardly and horizontally from the end of the inside vertical portion.

The present invention provides also a package obtained by theabove-described method of manufacturing a gas displacement package.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a container and a lid.

FIG. 2 is a perspective view of the container and the lid overlappedeach other.

FIG. 3 is a sectional view of the container and the lid overlapped eachother.

FIG. 4 shows a flange of a receptacle in FIG. 1, in which FIG. 4(a) is aplan view and FIG. 4(b) is a front view.

FIG. 5 illustrates a recess shape in a horizontal portion and a verticalportion shown in FIG. 4, in which FIG. 5(a) shows a triangle in thehorizontal portion, FIG. 5(b) shows a semicircle or a semi-ellipse inthe horizontal portion, and FIG. 5(c) shows a trapezoid in thehorizontal portion.

FIG. 6 is a perspective view of a configuration example with a step anda reinforcing surface formed in a configuration shown in FIG. 3(a).

FIG. 7 is a plan view of a part of the flange of the receptacle shown inFIG. 6.

FIG. 8 shows examples of shapes of a hole and an adhesive label.

FIG. 9 is perspective views of a gas displacement method according tothe present invention.

FIG. 10 is a perspective view of a receptacle used in the examples.

FIG. 11 is a perspective view of a lid used in the examples.

FIG. 12 is a perspective view of the receptacle and the lid used in theexamples overlapped each other.

FIG. 13 is a perspective view of sealing with a band tape in theexamples.

FIG. 14 is a perspective view in which the ridges of the receptacle andthe lid are overlapped and sealed with the band tape.

FIG. 15(a) is a perspective view in which the overlapped ridges of thereceptacle and the lid are sealed with the band tape in a clockwisedirection, and sealing has been completed with an end of the band tapebeing not adhered to the receptacle and the lid, FIG. 15(b) is aperspective view in which the end of the band tape not adhered to thereceptacle and the lid is being pulled for unsealing, and FIG. 15(c) isa schematic diagram of ends of the band tape in FIG. 15(a) overlappedeach other, seen from the above.

FIG. 16 shows an example in which the same receptacle and the lid asshown in FIG. 15 are used and a cutout is formed at a side along thelength of the band tape. FIG. 16(a) is a perspective view in which theband tape with the cutout is used, and sealing has been completed, FIG.16(b) is a perspective view in which the ends of the band tape are beingpulled to cause cutting at the cutout of the band tape for unsealing,and FIG. 16(c) is a schematic diagram of the ends of the band tape inFIG. 16(a), seen from the above. and

FIG. 17 shows an example in which the same receptacle and the lid asshown in FIG. 15 are used and a cut tape is provided in parallel withthe length of the band tape and at the center of the width of the bandtape. FIG. 17(a) is a perspective view in which the band tape with thecut tape in parallel with the length is used, and sealing has beencompleted, and FIG. 17(b) is a perspective view in which an end of thecut tape of the band tape is being pulled to separate the band tape intotwo at the center by the cut tape (upper and lower sides of theseparated band tape are still attached to the receptacle and the lid)for unsealing the container.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, preferred embodiments of the present invention will be described indetail. First, a container used in the present invention will bedescribed.

The container of the present invention includes a receptacle and a lid,which may be made of any materials. For example, the materials mayinclude plastic, metal, wood, paper, etc. alone, or lamination of suchmaterials. The lid of the present invention is shaped to cover a top ofthe receptacle, and may be made of the same materials as the receptacle.In particular, plastic is preferable because it is clear and allows acontent to be visible, has a high gloss, a good appearance, and a goodfractional recovery system in disposing of. A gas barrier plasticdescribed later is more preferable in view of preventing gas dispersion.In order to display the container such that it looks as if it contains alarge volume of content, it is preferable to form the receptacle to havea smaller height than the lid covering the top. A shape of an opening ofthe receptacle according to the present invention may be a circle, apolygon such as a triangle, a box (rectangle, square), or a rhombus, oran indefinite shape such as an ellipse, or a curve.

The container is used in such a manner that it is sealed with the bandtape, that is, the band tape is adhered over both edges of thereceptacle and the lid.

An overlapping portions of the receptacle and the lid of the presentinvention means a portion at which edges of the openings of thereceptacle and the lid overlap each other to close. The shapes of theedges may be linear or curved, or may be along or not along the shape ofthe receptacle as long as both edges can overlap each other to close.The overlapping portion is not necessarily provided at the entire edgesas long as the container can be sealed when the band tape is adhered,but is preferably provided at an entire periphery. Parts of thereceptacle and the lid may be joined via a hinge.

In order to efficiently and mechanically perform sealing, and to keepstiffness of the container, it is preferable that the overlappingportion has flanges and they are shapes to be overlapped at the flanges.With the flanges, attaching the band tape to ends of the flanges, thatis, ends of vertical portions easily provides a stable seal.

The flanges refer to entire portions extending from the edges of theopenings of the receptacle and the lid, and correspond to brim portionsat which the receptacle and the lid overlap each other (for example,reference numeral 11 and 21 in FIG. 1). The flanges comprise horizontalportions (reference numeral 12 and 22 in FIG. 1), vertical portions(reference numeral 13 and 23 in FIG. 1), and ridges at boundariesbetween the horizontal and vertical portions (reference numeral 14 and24 in FIG. 1).

The horizontal portions are surfaces substantially horizontallyextending from the edges of the openings of the receptacle and the lid.The horizontal portions may be tilted or have slight variations inthicknesses of materials as long as they are substantially horizontal.

The vertical portions (reference numeral 13 and 23 in FIG. 1) aresurfaces substantially vertically extending from the horizontalportions. The vertical portions may be tilted as long as they aresubstantially vertical. The direction of the extending may be upwardlyor downwardly from the horizontal portion, or the vertical portion ofthe lid may be extended upwardly and the vertical portion of thereceptacle may be extended downwardly. It is preferable, however, boththe vertical portions of the receptacle and the lid extend downwardlybecause with such structure, dust and litter hardly enter from theoverlapped portions.

As described above, providing the flange with the vertical portionallows the band tape to be stably attached to the vertical portion evenwhen mechanically attached using an attachment device etc. At this time,it is preferable to provide a difference between lengths of the verticalportions of the lid and the receptacle because the band tape can beattached over both ends of the flanges and attached even to corners ofthe container without wrinkles. Especially, when an attachment devicethat operates at high speeds is used for attaching, it is effective thatthe vertical portion which is inside the container is longer than thevertical portion which is outside the container. Specifically, when thevertical portions are extended downwardly from the horizontal portions,the vertical portion of the receptacle is formed to be longer than thevertical portion of the lid, while when the vertical portions areextended upwardly from the horizontal portions, the vertical portion ofthe lid is formed to be longer than the vertical portion of thereceptacle. This shape of the container causes no wrinkles of the bandtape at the corners of the container, and no reduction in sealingperformance. When sealing is carried out by using a packaging device,even if shape or size of the container is changed, it is possible tocope with such change only by changing the width of the band tape orattaching position of the band tape set in the packaging device, thuseliminating the need for providing sealing parts for each container.

Further, when the longer vertical portion is provided with a step(reference numeral 81 in FIG. 6) having a depth enough to accommodate athickness of the shorter vertical portion, the vertical portions becomeflat to allow the band tape to be attached in a flat manner, thusfacilitating work, increasing strength as a package, and facilitatinghandling of the package.

The vertical portion may have a length such that the band tape can beattached over the portion, and the length is not limited, but ispreferably 2 mm to 35 mm because the lid and the receptacle are noteasily displaced when the tape is attached, thus facilitating attachmentof the tape, increasing stiffness of the flange, and improving theappearance. The length is more preferably 3 mm to 30 mm, and furtherpreferably 4 mm to 25 mm.

If the vertical portions of the receptacle and the lid are extended inopposite directions, it is preferable to provide a recess or aprojection for positioning at the flange. Any locations or sizes may bepossible as long as the receptacle and the lid are not displaced whenthe band tape is attached to the boundary between the lid and thereceptacle. The recess or the projection is preferably provided near theopening of the container, especially at corners inside the receptacle inview of appearance or ease of taking out the content. It is alsopreferable to provide a recess at the horizontal portion of thereceptacle and a projection at the horizontal portion of the lid.

Further, it is preferable to form a recess (reference numeral 15 inFIG. 1) at the flange in order to increase strength of the flange. Thiseliminates the possibility of deformation of the flange by an externalforce applied when the band tape is attached, and prevents reduction inthe appearance or sealing performance caused by the deformation.

Further, the flange may have a fitting thread. The fitting thread meansa shape having grooves for fitting the receptacle to the lid at theridges of the receptacle and the lid. The providing manner of thefitting thread is roughly divided into three kinds: outer fitting, innerfitting, and inner and outer fitting. The outer fitting is a structurenot requiring high accuracy of a mold for forming the container, and isinexpensive and easy. On the other hand, the inner fitting requireshigher accuracy of the mold in forming the container in comparison withthe outer fitting, and is expensive, but when the content is delisubstances containing juice, it can prevent leakage of the juice out ofthe container. Further, the inner and outer fitting requires highaccuracy of the mold in forming the container, and is very expensive,but is the highest level fitting that provides high fitting strength ata fitting portion and prevents separation of the lid from the receptacleeven when some impact is applied.

The packaging container has a hole. The hole has to be a channel throughwhich gas flows into and out of the packaging container which thereceptacle and the lid are sealed, and is different from a clearancebetween a receptacle and a lid in a prior art gas displacement methodusing a chamber. A size or a shape of the hole, or the number of holesmay be such that the gas can flow into and out of the packagingcontainer. The hole is preferably provided on the lid in view of ease ofclosing the hole after the gas displacement or preventing leakage of thecontent, and more preferably on the top of the lid.

An opening area of the hole is preferably 0.3 to 3 cm² with respect to avolume of the content of 1000 cm³ in the packaging container.

The opening shape of the hole may be such that the gas can flow into andout of the packaging container. For example, the opening shapes of thehole may include a cutout shape having a complete opening such as asquare (A in FIG. 8), a rectangle (B in FIG. 8), a rounded rectangle (Cin FIG. 8), a polygon (D in FIG. 8), a circle (E in FIG. 8), asemi-circle (F in FIG. 8), an ellipse (G in FIG. 8), a semi-ellipse (Hin FIG. 8), a star (I in FIG. 8), and an indefinite shape (J in FIG. 8),or a cutout shape having an incomplete opening such as a quasi-horseshoeshape (O in FIG. 8), a V shape (P in FIG. 8), a U shape (Q in FIG. 8), aC shape (R in FIG. 8), and an indefinite shape (S in FIG. 8). Thesecutout shapes are preferable because they cause no cuttings in boringthe hole in the lid.

An area of the cutout hole is represented by the largest area when atongue in the cutout is folded to open the hole. The opening area of thehole differs depending on the volumes of the contents. However, if theopening area of the hole is 0.3 cm² smaller with respect to the volumeof the content of 1000 cm³ in the packaging container, resistance whenair or the desired gas flows in or out of the packaging containerthrough the hole becomes large because a large amount of gas moves inand out of the packaging container in a short time when the chamber isdeaerated or the packaging container is filled with a desired gas. Dueto such resistance, a difference in atmospheric pressure between theinside and the outside of the packaging container is resulted andsometimes deformation of the packaging container occurs.

If an opening area of the hole goes over 3 cm², the deaeration and thegas displacement can be performed easily, but it is needed to enlarge anarea of the adhesive label for closing the hole. This sometimescompromises the appearance of the packaging container, and reducesmechanical strength of the opening of the adhesive label attached overthe hole. Thus, the opening area of the hole is preferably 0.3 to 3 cm²,more preferably 0.4 to 2.8 cm², and further preferably 0.6 to 2.5 cm².

The number of holes is preferably as small as possible such that theholes are closed by one adhesive label, in view of ease of closing theholes and appearance of the packaging container. However, even in a casewhere a large number of holes are provided, by collectively providing aplurality of small holes at one place, it is possible to close the smallholes by one adhesive label, so that mechanical strength of the adhesivelabel is increased. Accordingly, this is preferable.

Usually, the hole is created in a different process from the forming,and an example of creating the hole will be described. First, a plasticsheet is thermally molten, and formed in conformity with a mold, andsheet-like continuous formed products are pressed and cut out by acutting blade called a cutting die.

As a methods of closing the hole, various methods such as attaching theadhesive label or filling the hole can be considered, but closing thehole by the adhesive label is preferable in view of the appearance ofthe container and convenience. More preferably, a print may be made onthe adhesive label for product differentiation. Materials for theadhesive label will be described later.

Now, the present invention will be described below with reference to thedrawings.

FIG. 1 shows a perspective view of an embodiment of a packagingcontainer according to the present invention. In the drawing, referencenumeral 10 denotes a receptacle; 11, flange; 12, horizontal portion; 13,vertical portion; 14, ridge; 15, recess; 20, lid; 21, flange; 22,horizontal portion; 23, vertical portion; 24, ridge; 40, hole; and 50,adhesive label.

The packaging container comprises the receptacle 10 and the lid 20, andthe receptacle 10 has the flange 11 at an opening, and the lid 20 hasthe flange 21 that is overlapped on the flange 11. FIG. 2 is aperspective view showing a state in which a content is put in thereceptacle 10 of the packaging container, the lid 20 is placed on thereceptacle 10, and the vertical portions are sealed with a band tape. Inthe drawing, reference numeral 30 denotes the band tape; 40, hole; and50, adhesive label.

The flange 11 of the receptacle 10 has the horizontal portion 12horizontally extending from a periphery of the opening of the receptacle10, and the vertical portion 13 vertically extending from an end of thehorizontal portion 12. The flange 21 has the horizontal portion 22 andthe vertical portion 23 correspondingly to the flange 11. The receptaclehas, at part of the ridge 14, the recess 15 formed in such a manner thatthe vertical portion 13 is dented inwardly and the horizontal portion 12is dented downwardly. Likewise, a recess may be formed on the flange 21of the lid in such a manner that the vertical portion 23 is dentedinwardly and the horizontal portion 22 is dented upwardly at the ridge24 formed by the horizontal portion 22 and the vertical portion 23. Therecess 15 is provided in order to increase stiffness of the flange 11,and may be provided at a portion other than corners of the flange, butmay be provided on the corners as desired. The number of recesses 15 isnot limited.

FIG. 3 shows an example of the flanges 11, 12. FIG. 3(a) is a partialenlarged sectional view taken along a line A-A′ in FIG. 1, and shows anexample in which the vertical portions 13, 23 are vertically anddownwardly extended from the ends of the horizontal portions 12, 22. Inthis configuration, the vertical portion 13 of the receptacle 10 placedinside is formed to be longer than the vertical portion 23 of the lid20. FIG. 3(b) shows an example in which the above described inner andouter fitting is provided in the example of FIG. 3(a). A protrusion 17and a groove 27 fitting over the protrusion 17 are formed in thehorizontal portions 12, 22 of the receptacle 10 and the lid 20 inparallel to the peripheries of the openings to strengthen the flanges11, 21.

FIG. 4 is enlarged views of the flange 11 of the receptacle 10 shown inFIG. 1. FIG. 4(a) is a plan view of the flange (a top view of thehorizontal portion), and FIG. 4(b) is a front view of the flange (afront view of the vertical portion). The dotted line in the front viewof FIG. 4(b) indicates a position to which the vertical portion of thelid overlaps.

A size of the recess 15 depends on a size or strength of the flange 11,but when in general the receptacle is used as a packaging container forfood products, it is preferable that the recess 15 may be a rectangle inthe horizontal portion 12 and the vertical portion 13 as shown in FIG.4. In this case, it is preferable that a width (W) of the recess 15 is 1to 20 mm, a distance (S) between adjacent recesses 15 is 3 to 20 mm, anda depth from the vertical portion 13 is set such that a clearance (d)remaining in a width (D) of the horizontal portion 12 is 1 mm or moreand ⅕ to ⅘ of the width (D). A depth (T) from the horizontal portion 12is set such that a clearance (t) between the recess 15 and the end ofthe vertical portion 23 of the flange 21 of the lid 20 indicated by thedotted line is 0.5 mm or more and ½ or less of a width (H) of thevertical portion 13. A relationship between a width (H) of the verticalportion 13 and the depth (T) is set such that (H-T) leaves an enoughwidth to attach the band tape. When the recess 15 is provided on theflange 21 of the lid 20, in the above-described setting, the term“flange 11” may by replaced by the term “flange 21”.

The shape of the recess 15 may be, besides the rectangles in thehorizontal portion 12 and the vertical portion 13 as shown in FIGS. 1and 4, a triangle as shown in FIG. 5(a), a semi-circle or a semi-ellipseas shown in FIG. 5(b), or a trapezoid as shown in FIG. 5(c) in thehorizontal portion 12. In addition, in the case shown in FIG. 5(a), atop angle (θ) in the horizontal portion 12 is preferably 20 to 150°, andin the case shown in FIG. 5(c), a width (w) of a top side is preferably1 to 18 mm. In either case, it is preferable that a depth from thevertical portion 13 is set such that a clearance (d) remaining in thewidth (D) of the horizontal portion 12 is 1 mm or more and ⅕ to ⅘ of thewidth (D). Further, a width (W) in the vertical portion 13, a distance(S) between the adjacent recesses 15, and a depth from the horizontalportion 12 are the same as in the rectangle shown in FIG. 4(a).

In the packaging container, in order to prevent the lid 20 from slippingoff the receptacle 10, one of the flanges 11, 21 of the receptacle 10and the lid 20 may have a protrusion extending toward the other, and theother of the flanges 11, 21 may have a recess receiving the protrusion.

FIG. 6 shows an application example of the receptacle shown in FIGS.3(a) and 3(b), in which a step 81 extending outwardly in a horizontaldirection is formed on the vertical portion 13 at a position below theend of the vertical portion 23, and a reinforcing surface 82 extendingoutwardly in the horizontal direction from the end of the verticalportion 13 is formed. FIG. 7 is a partial plan view of the flange of thereceptacle shown in FIG. 6. A width (p1) of the step 81 is preferablywithin ±2 mm of a thickness of the vertical portion 13 of the flange 11of the lid 20. By providing the step 81, a step, which is formed on asurface of the band tape by the end of the vertical portion 23 when theband tape is attached, is made to be gentler, thus improving theappearance. The step 81 is preferably placed near the vertical portion23 of the lid 20, and more preferably within 2 mm from the end of thevertical portion 23. A width (p2) of the reinforcing surface 82 ispreferably set within 1 to 2 mm because a width less than 0.5 mminsufficiently increases the stiffness, and a width more than 2 mmcompromises the appearance.

It is preferable that when the receptacle and the lid of the presentinvention are made of thermoplastic resin, a resin sheet previouslycreated is formed by a known thermoforming method (such as air pressureforming, vacuum forming, vacuum air pressure forming).

When the receptacle and the lid are formed from the resin sheet, anyresins that are generally used for receptacle and lids may be used. Forexample, thermoplastic resins include a polyethylene resin, apolypropylene resin, a polystyrene resin, a methacrylate resin, apolyvinyl chloride resin, a polycarbonate resin, a cellulose acetateresin, and the like. When a gas barrier property is required,thermoplastic resins include a polyamide resin, a polyethyleneterephthalate resin, a polybutylene terephthalate resin, anethylene-vinyl alcohol copolymer resin (EVOH), and the like. Thereceptacle and the lid are made of a single layer sheet or a multilayersheet made of such resins. Methods for forming a multilayer includecoextruding, various kinds of laminating, etc. and may be appropriatelyselected.

The sheet used in the present invention may be made of a material havingthe gas barrier property in accordance with need.

The band tape in the present invention will now be described. The bandtape in the present invention is a shape elongated with a width, and canseal the packaging container by being attached over flange surfacesextending from the receptacle and the lid. The band tape has an adhesiveon a surface to be brought into contact with the packaging container. Aslong as the receptacle and the lid can be sealed without any clearances(tightly sealed) by the adhesive, the band tape may have a constantwidth or a varying width.

Materials for the band tape may include a single layer or a multilayerof paper, metal thin films, and resin, but materials including metalsuch as a metal thin film or a metallized film are not preferable inview of preventing spark caused by electron collision in heating by amicrowave oven, and the same material as the packaging container ispreferable in view of fractional recovery. A gas barrier resin isfurther preferable in order to prevent gas dispersion from the clearancebetween the lid and the receptacle.

The gas barrier band tape may be made of, for example, two layers of agas barrier base layer and an adhesive layer.

The gas barrier base layer may be provided with a gas barrier resin or aresin layer having a laminated inorganic substance. As the resin layerhaving a laminated inorganic substance, for example, a resin layer canbe considered in which an inorganic substance of silica and/or aluminais vapor deposited on a low density polyethylene resin layer, of whichgas barrier property is poor, to provide gas barrier properties.

The gas barrier base layer preferably has an amount of transmission ofcarbon dioxide gas of 1.0 to 4935.0 ml/m²/day MPa, an amount oftransmission of oxygen gas of 1.0 to 3948.0 ml/m²/day/MPa, and an amountof transmission of nitrogen gas of 1.0 to 1480.5 ml/m²/day/MPa, morepreferably has an amount of transmission of carbon dioxide gas of 10.0to 4500.0 ml/m²/day MPa, an amount of transmission of oxygen gas of 10.0to 2500.0 ml/m²/day/MPa, and an amount of transmission of nitrogen gasof 10.0 to 1300.0 ml/m²/day/MPa, and further preferably has an amount oftransmission of carbon dioxide gas of 20.0 to 4000.0 ml/m²/day MPa, anamount of transmission of oxygen gas of 20.0 to 1300.0 ml/m²/day/MPa,and an amount of transmission of nitrogen gas of 20.0 to 1000.0ml/m²/day/MPa. More preferably, the gas barrier base layer has an amountof transmission of carbon dioxide gas of 20.0 to 1000.0 ml/m²/day MPa,an amount of transmission of oxygen gas of 20.0 to 300.0 ml/m²/day/MPa,and an amount of transmission of nitrogen gas of 20.0 to 250.0ml/m²/day/MPa.

The gas barrier base layer resin preferably has an amount oftransmission of oxygen gas of 1.0 to 1974.0 ml/m²/day/MPa. Gas barrierbase layer resins may include, for example, a single layer or amultilayer of a resin compound that is composed exclusively of at leastone of the followings: a polyolefin resin (PO) such as a polyethyleneresin (HDPE, LLDPE, etc.), a polypropylene resin (PP), a polybutene-1resin (PB), and a poly-4-methylpentene-1 resin; a polyolefin modifiedresin (PO modified resin) such as an ethylene-vinyl acetate copolymerresin (EVA), an ethylene-methyl methacrylate copolymer resin (EMA etc.),an ethylene-vinyl alcohol copolymer resin (EVOH etc.); a polyester resin(PEST) containing in part an aromatic component such as a polyethyleneterephthalate (including modification) resin (PET etc.), or apolybutylene terephthalate (including modification) resin (PBT etc.), orcontaining an aliphatic component such as a polylactic acid resin, or apolyglycol acid resin; a chlorine resin such as a polyvinylidenechloride resin (PVDC), or a polyvinyl chloride resin (PVC); an alphaolefin-carbon monoxide copolymer resin (including a hydrogenated resinthereof); an alpha olefin (ethylene etc.)-styrene copolymer resin(including a hydrogenated resin thereof); an ethylene-cyclic hydrocarboncompound copolymer resin (including a hydrogenated resin thereof); apolyamide resin (Ny); and a caprolactone resin, or lamination of resinsdifferent from the layers, or a drawn or undrawn tape made of theseresins. In particular, the polyester resin (PEST) containing in part thearomatic component such as the polyethylene resin (especially HDPE), thepolypropylene resin (PP), the ethylene-vinyl alcohol copolymer resin(EVOH etc.), the polyamide resin (Ny), the polyethylene terephthalate(including modification) resin (PET etc.), or the polybutyleneterephthalate (including modification) resin (PBT etc.), or containingthe aliphatic component such as the polylactic acid resin, or thepolyglycol acid resin are preferable in view of heat resistance and thegas barrier property. Known additives, for example, an antioxidant, alight stabilizer, an antistatic agent, an anti-fogging agent, a coloringagent, or a lubricant may be mixed, or known surface treatments, forexample, a corona discharge treatment, a flame treatment, an irradiationtreatment of electron and plasma, an ion etching treatment, or a gasbarrier coating treatment of vinylidene chloride etc. may be performed.

The thickness of the gas barrier base layer differs depending on amountsof transmission of oxygen gas of the resin to be used, and a preferablethickness is such that the amount of transmission of oxygen gas is 1.0to 1974.0 ml/m²/day/MPa. For example, in the case of the ethylene-vinylalcohol copolymer resin (EVOH) that has a small amount of transmissionof oxygen gas, a required amount of transmission of oxygen gas can bereached in some μm in view of the amount of transmission of oxygen gas,but the resin has low stiffness as the band tape, thus may be laminatedwith other resins having stiffness. Such resins include, for example,the polypropylene resin (PP). For the gas barrier base layer made oflamination of PP and EVOH, the amount of transmission of oxygen gas ispreferably 1.0 to 1974.0 ml/m²/day/MPa, and the thickness of the gasbarrier base layer is preferably 15 to 100 μm in view of stiffness ofthe band tape. The thickness is more preferably 20 to 90 μm, and furtherpreferably 25 to 85 μm.

Adhesion in the present invention means bonding of the band tape, andthe receptacle and the lid. Adhesion strength can be appropriatelyselected, and typical adhesives are of a solvent type, a hot melt type,a reactive type, etc. However, any adhesives can be used, and when thecontent is a food product, adhesives that comply with the FoodSanitation Law are preferably used. The adhesives include, for example,a rubber adhesive, an acrylic adhesive, a vinyl ether adhesive, asilicone adhesive, or a resin compound that is composed exclusively ofat least one of them. In view of ease of setting desired adhesivestrength, the rubber adhesive, the acrylic adhesive, and the vinyl etheradhesive are preferable, and the rubber adhesive and the acrylicadhesive are more preferable. In view of reduced solvent extracts andreduced impurities, the acrylic adhesive is further preferable.

The adhesives may contain known additives, for example, an antioxidant,a light stabilizer, an antistatic agent, an anti-fogging agent, or acoloring agent, without compromising the advantage of the presentinvention. In order to produce partial separation between the gasbarrier base layer and the adhesive layer of the adhesive label for gasdisplacement packaging and sealing, a silicon print having a separationeffect is previously made on the gas barrier base layer, and so-called atampering prevention print may be made in which the adhesive layer isseparated from the gas barrier base layer, and remains on the receptacleand the lid to which the adhesive layer adheres.

The rubber adhesive may include, for example, at least one adhesiveelastomer selected from a natural rubber exclusively composed ofcis-1,4-polyisoprene; a synthetic rubber exclusively composed of astyrene-butadiene rubber (SBR), poly isobutylene, butyl rubber, etc.; ora block rubber exclusively composed of a styrene-butadiene-styrenecopolymer rubber (SBS), styrene-isoprene-styrene copolymer rubber (SIS),etc., mixed with an adhesive attaching agent such as a rosin resin, aterpene resin, a petroleum resin, or a chroman-indene resin that is athermoplastic resin of an amorphous oligomer (middle molecule weightcopolymer more than a dimmer) having a molecular weight of some hundredsto about ten thousands in liquid or solid at room temperature, and asoftener such as mineral oil, liquid polybutene, liquid polyisobutylene,liquid polyacrylic ester, etc.

The acrylic adhesive may include, for example, an adhesive reactant of amain monomer that provides adhesion such as acrylic acid alkyl esterthat is a homopolymer generally with low Tg; a comonomer that can becopolymerized with the main monomer and provide cohesiveness to increaseTg, such as acrylic acid ester of a lower alkyl group, methacrylic acidalkyl ester, vinyl acetate, styrene, acrylonitrile; a monomer containinga carboxyl group such as acrylic acid or methacrylic acid (acrylateetc.); and a monomer containing a functional group that providesadhesion and becomes a crosslinking point such as a hydroxyl group, anepoxy group, or an amino group, mixed with the adhesive attaching agent,the softener, etc. in some cases.

The vinyl ether adhesive may include, for example, a homopolymer such asvinyl methyl ether, vinyl ethyl ether, or vinyl isobutyl ether, or acopolymer (an adhesive elastomer) with acrylate, mixed with the adhesiveattaching agent, the softener, etc. in some cases.

The silicone adhesive may include, for example, a polymer (or anadhesive elastomer) having a residual silanol group (SIOH) at a terminalof a polymer chain such as polydimethyl siloxane or polydimethyldiphenyl siloxane with a high molecule weight, mixed with the adhesiveattaching agent, the softener, etc.

The synthetic rubber adhesive or the acrylic adhesive are preferablebecause the adhesive strength can be set in a wide range in view of thegas barrier property, especially the gas displacement packaging, and inview of food sanitation.

The adhesive strength is preferably 0.1 to 15 N/cm in a measuring methodby a 180 degrees peeling test of JIS-Z-0237 in view of adhesive strengthin adhesion and peeling strength in peeling. The adhesive strength ismore preferably 0.2 to 13 N/cm, and further preferably 0.3 to 12 N/cm.

The thickness of the adhesive layer differs depending on adhesives to beused, but the adhesive strength may be 0.1 to 15N/cm and does not dependon the thickness of the adhesive layer. For example, in the case of therubber adhesive or the acrylic adhesive, the thickness of the adhesivelayer is preferably 3 to 70 μm in view of the adhesive strength. Thethickness is more preferably 5 to 60 μm, and further preferably 8 to 55μm.

The band tape preferably has a certain degree of strength and elongationin view of mechanical suitability when the tape is attached by amachine. In a measurement based on an adhesive tape test of JIS-Z-0237,tensile strength is preferably 10 to 120 N/10 mm, more preferably 20 to110 N/10 mm, and further preferably 25 to 95 N/10 mm. The band tapeitself preferably has flexibility in order for the band tape to beadhered to the corners of the receptacle and the lid without any gasdispersion area (clearance) such as wrinkles. In an elasticitymeasurement of a 100 mm long band tape (10 mm wide) under a condition oftensile rate of 5 mm/min, the elasticity is 3 to 150 kg/mm², morepreferably 5 to 130 kg/mm², further preferably 7 to 110 kg/mm², in viewof an adhesion state of the band tape to the receptacle and the lid.

Further, in the case where the band tape is attached to the packagingcontainer to seal the entire periphery, seal is realized by overlappingthe band tape once wound around the packaging container on a front endthereof (FIG. 158 c)). When the band tape once wound around thepackaging container is overlapped on the front end of the band tape, aslight clearance is sometimes created along the width of the band tapedepending on the thickness of the front end of the band tape. To fillthe clearance, sealing performance may be increased by smoothing theband tape with a spatula to move the adhesive layer, or covering theband tape with a hot melt agent, or various gas barrier films.

The band tape 30 may have a function of easy opening. For example, theband tape is provided with a narrow portion such as a cutout (FIG. 16).Upon opening, the band tape is broken at the narrow portion.Alternatively, the band tape is provided with a string-like cut tape 60in parallel with the length of the band tape at a center of the width ofthe band tape (FIG. 17). Upon opening, the band tape sealing the flangesof the receptacle and the lid is separated into two at the center by thecut tape 60 (upper and lower ends of the separated band tape are stillattached to the receptacle and the lid) to easily open the package. Withthese structure, the packaging container can be easily opened.

The adhesive label will be described. The adhesive label preferablycontains a gas barrier material. The hole is closed by the label to sealso as to prevent a desired gas in the packaging container from beingdispersed. Thus, the adhesive label requires tight contact with thereceptacle and the lid. The adhesive label may only require tightcontact, which may be any of sealing, bonding, or adhesion.

The adhesive strength of the adhesive label may be appropriatelyselected, and the kind or the amount of application of the adhesive maybe selected depending on desired adhesive strength. The same adhesivesas used for the band tape may be used, but for use of cooking by amicrowave oven, an adhesive label using an adhesive of the water ororganic solvent type or the hot melt type that has a tendency to reducethe adhesive strength with increase in temperature in the packagingcontainer is preferable in view of preventing water vapor blowout causedby increase in internal pressure of the packaging container resultingfrom heating by the microwave oven. The adhesive of the water or organicsolvent type or the hot melt type are more preferable since they havesafety in food sanitation. The adhesive label can have any shapes aslong as it can close the hole, regardless of opening shape of the hole.For example, the shapes may include a square (A in FIG. 8), a rectangle(B in FIG. 8), a rounded rectangle (C in FIG. 8), a polygon (D in FIG.8), a circle (E in FIG. 8), a semi-circle (F in FIG. 8), an ellipse (Gin FIG. 8), a semi-ellipse (H in FIG. 8), a star (I in FIG. 8), and anindefinite shape (J in FIG. 8), and a circle (K in FIG. 8), a rectangle(L in FIG. 8), and an ellipse (I in FIG. 8) with a tab. For the lid madeof the resin sheet, uneven portions may be created near the hole toincrease stiffness of the lid when the adhesive label is attached.

Materials of the adhesive label may include a single layer or amultilayer of paper, metal thin films, or resin, but materials includingmetal such as a metal thin film or a metallized film are not preferablein view of preventing spark caused by electron collision in heating by amicrowave oven, and the same material as the packaging container ispreferable in view of fractional recovery. A gas barrier resin isfurther preferable in order to prevent gas dispersion.

The material having the gas barrier property, the configuration, thethickness, and the performance may be the same as described above withrespect to the band tape.

The adhesive strength of the adhesive tape is preferably 0.1 to 10 N/cmin a measuring method by a 180 degrees peeling test at 25° C. ofJIS-Z-0237 (the 180 degrees peeling test of JIS-Z-0237: a 25 mm widetape is attached to a stainless plate, one end of the tape is peeled offfrom the test plate toward the other end in a 180 degrees direction at apeeling rate of 300 m/min, and a force required for the peeling ismeasured and used), in view of the adhesive strength upon adhesion andthe peeling strength upon peeling. The adhesive strength is preferably0.2 to 9.5 N/cm, and more preferably 0.3 to 7.5 N/cm. A measured valueby the 180 degrees peeling test at 80° C. is preferably lower than ameasured value by the 180 degrees peeling test at 25° C. in view of theadhesive label automatically peeling off by the increase in the internalpressure of the packaging container. The measured value by the 180degrees peeling test at 25° C. is preferably 0.1 to 8 N/cm in view ofthe adhesive strength upon adhesion and the peeling strength uponpeeling. The measured value is more preferably 0.2 to 7.5 N/cm, andfurther preferably 0.3 to 5.5 N/cm.

The thickness of the adhesive layer differs depending on the adhesivesto be used, but the adhesive strength may be 0.1 to 10N/cm in themeasuring method by the 180 degrees peeling test at 25° C., and does notdepend on the thickness of the adhesive layer. For example, in the caseof the rubber adhesive or the acrylic adhesive, the thickness of theadhesive layer is preferably 2 to 10 μm in view of the adhesivestrength. The thickness is more preferably 3 to 90 μm, and furtherpreferably 5 to 85 μm.

The gas barrier adhesive label has a certain degree of strength in viewof preventing breakage caused by external puncture. In a measurementbased on Article 10 of the Japan Agriculture Standard, puncture strengthis preferably 2.0 N and more, more preferably 2.5 N and more, andfurther preferably 3.0 N and more. Further, the adhesive label may havea tab for ease of opening. For example, it is preferable in view ofprevention of blowout in heating the packaging container that theadhesive label has a semi-circular tab which is pulled up from the lidto easily open the packaging container for ease of opening.

Main contents of the packaging container are cooked food products, forexample, delis (boiled, baked, steamed, or fried foods) or boxed mealssold at supermarkets or convenience stores.

Now, a packaging method according to the present invention will bedescribed.

The packaging method according to the present invention is a gasdisplacement sealing method in which the hole 40 is used to performdeaeration and gas displacement in a chamber, and the hole is closedafter the gas displacement. Thus, gas in a space or the content in thepackaging container is displaced by a desired gas. Specifically, afterdeaerating the chamber, gas displacement is performed by an inert gas,thereby causing deaeration and gas displacement in the packagingcontainer via the hole provided on the container. The deaeration and thegas displacement in the chamber substantially eliminate a difference inatmospheric pressures between the inside of the packaging container andthe inside of the chamber (the outside of the packaging container) toprevent the packaging container from being crushed by the difference inthe atmospheric pressures.

The gas displacement means that air in the packaging container isdisplaced by a desired gas, which contributes to increase in shelf lifeof the contents and to prevent color variation of the product. Forexample, holding food products in an inert gas atmosphere contributes to(1) preventing oxidation of oil and fat content, (2) preserving activeingredients such as vitamins, (3) preventing rot caused by developmentof mold, bacteria, or yeast, (4) preventing discoloration and fading,and (5) preventing loss of flavor, etc. Further, displacement by a gassuch as carbon dioxide having bacteriostasis can sometimes increase theshelf life of the contents.

Any gases generally known can be used in the present invention. Forexample, nitrogen, carbon dioxide, oxygen, argon, etc. can be used aloneor in combination thereof. Ozone or natural and synthetic antibacterialsubstances (for example, hinokitiol) generally known as bactericide formold, bacteria, or yeast may be used.

As a method of deaeration and gas displacement in the chamber, a generalchamber type gas displacement method can be used. Generally known gasdisplacement methods are of the chamber type and the gas flushing type.FIG. 9 shows a chamber type gas displacement method according to thepresent invention. The chamber type gas displacement method according tothe present invention is a method in which the packaging container, ofwhich the receptacle 10 and the lid 20 (hole 40) are sealed with theband tape 30, is placed in the space in the chamber (reference numeral70 in FIG. 9), the whole of the air in the chamber is expelled to bevacuum once (B in FIG. 9), and then a desired gas is fed into thechamber under vacuum for gas displacement. The adhesive label 50 isattached to the hole 40 of the lid 20 in the chamber to seal the spacein the packaging container (C in FIG. 9).

Generally, the chamber type gas displacement method can provide a highrate of gas displacement and reliable gas displacement, while the gasflushing type gas displacement method tends to provide a low rate of gasdisplacement though it is simple and inexpensive. The gas displacementmethod according to the present invention is of the chamber typedescribed above, and the air in the space and the contents in thepackaging container is reliably displaced by gas to increase the shelflife of the content and to prevent discoloration of the product, therebyallowing displacement in the packaging container at the high rate.

An example of a sealing method of sealing a packaging containercomprising the receptacle and the lid with a band tape according to thepresent invention will be described with reference to the drawings. Arectangular receptacle (FIG. 10) and a lid (FIG. 11) are used and ridgesof the receptacle and the lid (FIG. 12) overlap each other, and theridges are sealed with the band tape (FIG. 13). FIG. 13 is a perspectiveview showing a state in which the overlapping ridges of the receptacleand the lid are being sealed in a clockwise direction with the bandtape. FIG. 14 is a perspective view showing a state in which theoverlapping ridges of the receptacle and the lid have been sealed withthe band tape. The bonding direction of the band tape may be in theclockwise direction as shown or in the counterclockwise direction, aslong as the overlapping ridges of the receptacle and the lid can besealed with the band tape. As described above, the receptacle and thelid are sealed with the band tape, therefore receptacles and lids of anyshapes can be sealed with the band tape. Thus, this sealing method isexcellent.

An example of ease of opening will be described with reference to FIGS.15, 16, and 17. FIGS. 15, 16, and 17 show a process of causing only theridges of the rectangular receptacle and lid to overlap each other, andsealing the receptacle and the lid with the band tape having adhesion.The band tape in FIGS. 15, 16, and 17 is attached so as to achieve theease of opening, or the band tape itself is formed to achieve the easeof opening.

Examples shown in FIGS. 15, 16, and 17 will be described in detail. FIG.15(a) is a perspective view showing a state in which the overlappingridges of the rectangular receptacle and lid are sealed in the clockwisedirection with the band tape, and sealing has been completed with a rearend of the band tape being not adhered to the receptacle and the lid.FIG. 15(b) is a perspective view showing a state in which the rear endof the band tape not adhered to the receptacle and the lid is beingpulled for opening. FIG. 15(c) is a schematic diagram of ends of theband tape in FIG. 15(a) overlapping each other, seen from the above. Asmethods for giving no adhesive only to the rear end of the tape asdescribed above, there are a method in which a circumferential dimensionof the packaging container is previously measured, and only anoverlapping portion of the tape is not coated with an adhesive, and amethod in which a band tape across which an adhesive is applied is used,and adhesive surfaces at the rear end of the tape only are attached toeach other. The latter method is simple and preferable. FIG. 16 shows anexample in which the same receptacle and the lid as the example shown inFIG. 15 are used and a cutout at a side along the length of the bandtape is provided. Like the example shown in FIG. 15, FIG. 16(a) is aperspective view showing a state in which the band tape with the cutoutis used, and sealing has been completed. FIG. 16(b) is a perspectiveview showing a state in which the rear end of the band tape is beingpulled to cause breakage at the cutout of the band tape for opening.FIG. 16(c) is a schematic diagram of the ends of the band tape in FIG.16(a), seen from the above. As described above, pulling the rear endcauses the band tape to be cut from the cutout near the rear end of theband tape, thereby facilitating opening. The cutout of the band tape maybe created at part of the side of the band tape as shown in FIG. 16, ormay be created across the side or at both sides as long as the tape iscut when pulled. FIG. 17 shows an example in which the same receptacleand the lid as shown in FIG. 15 are used and a cut tape is provided inparallel with the length of the band tape at the center along the widthof the band tape. Like FIG. 15, FIG. 17(a) is a perspective view showinga state in which the band tape with the cut tape 60 in parallel with thelength is used, and sealing has been completed. FIG. 17(b) is aperspective view showing a state in which a rear end of the cut tape ofthe band tape with the cut tape in parallel with the length is beingpulled to separate the band tape into two at the center by the cut tape(upper and lower ends of the separated band tape are still attached tothe receptacle and the lid) for opening the packaging container. Themethod in which the cut tape is provide in parallel with the length ofthe band tape at the center of the width of the band tape, and the bandtape sealing the ridges of the receptacle and the lid is separated intotwo at the center by the cut tape to easily open the packaging containeris preferable in view of ease of opening. A color of the cut tape may bediffered from a color of the band tape for clarity.

Now, measuring methods and examples will be described in detail.

(1) Measuring an Amount of Transmission of Oxygen Gas

An amount of transmission of oxygen gas was measured in accordance withASTM-D-3985 (at a measurement temperature of 23° C.).

(2) Measuring a Percentage of Oxygen Composition in a Space in aPackaging Container A percentage of oxygen composition in a space in apackaging container at 23° C. and 50% RH was measured using Checkpointmanufactured by PBI-Dansensor A/S.

G (good): The percentage of oxygen composition in the space in thepackaging container after ten days is less than 1%.

M (moderate): The percentage of oxygen composition in the space in thepackaging container after ten days is 1% or more and less than 2%.

P (poor): The percentage of oxygen composition in the space in thepackaging container after ten days is 2% or more.

(3) Cooking Hamburgers

Minced beef and pork (5:5) of 1 kg and 2 middle size eggs were kneadedto become viscous while being cooled to 5° C. or less, and then 0.3 kgfried onion and 0.12 kg bread crumbs were added and further kneaded. Thekneaded materials were divided into 120 g portions, shaped into an ovalshape, placed in a 120° C. oven and heated until a central temperaturereaches 70° C. to cook hamburgers.

(4) Measuring a Preservation Temperature

A temperature was measured for every 10 minutes using Button Type CoolMemory manufactured by Sanyo Electric Co., Ltd. A cooked food productwas packaged, and then preserved in Open Showcase EA-MS manufactured byMitsubishi Electric Corporation (at a preservation temperature of 15°C.).

(5) Measuring General Viable Cell Count

A hamburger of 1 g was successively diluted with up to ten parts ofwater, and diluted sample solutions were prepared. Two deep petri disheswere provided for each dilution stage, and each diluted sample solutionwas poured into each dish by 1 ml. A standard agar medium of 15 ml thatis previously subjected to high pressure steam sterilization and thenheld at about 45° C. was aseptically poured into each dish, calmly mixedsuch that the diluted sample solution and the medium immediately mixedwell, and calmly left until the medium completely solidified. Theoperation from pouring the diluted sample solution into the dish tomixing with the medium was finished within 20 minutes, and when themedium solidified, the dish was inverted, a surface of the medium wasdried for 30 minutes in an incubator to perform cultivation at 35° C.for 48 hours. Then, the number of development colonies on a plate inwhich 30 to 300 cells developed was measured, the numbers of colonies ontwo plates were averaged and multiplied by multiples of dilution todetermine viable cell count for the food product of 1 g.

EXAMPLES 1 to 6

An undrawn barrier multilayer film was attached to a polypropylene resinsheet with filler for a receptacle, and a polystyrene resin sheet for alid, using a polyurethane dry laminate adhesive to form a multilayerresin sheet. The multilayer resin sheet was thermoformed into shapesshown in FIGS. 10 (the receptacle), 11 (the lid), and 12 (the lid placedon the receptacle). The lid was formed with a C-shaped hole having a 25cm diameter on a top thereof by a punch after forming and before drawinga formed product. Substantially vertical flanges of the receptacle andthe lid were sealed with a band tape shown in the examples. The volumein a packaging container was 800 cm³. The packaging container issubjected to vacuum and gas displacement using a chamber, air in thepackaging container was displaced by a high purity nitrogen gas (purity99.99%), the C-shaped hole on the lid was sealed with a circularadhesive label having a 35 cm diameter shown in the examples, and then,gas composition in the packaging container was measured immediatelyafter sealing, one day after the sealing, and 10 days after the sealing.The conditions and results will be shown in Table 1. Further, ahamburger as an example of a food product was placed in the packagingcontainer with the volume of 800 cm³ used in the examples of thepackaging container, and a mixed gas of carbon dioxide and nitrogen(1:1) was used to perform vacuum type gas displacement packaging. Somesamples prepared as described above were provided and preserved for aweek at various temperatures to determine general viable cell count atcertain times. The general viable cell count was determined for randomsamples selected from some samples provided under the same conditions.The conditions and the results will be shown in Table 1.

COMPARATIVE EXAMPLE 1

The same experiment as the examples was conducted except for using apolypropylene resin sheet with filler for the receptacle, and apolystyrene resin sheet for the lid. The conditions and the results willbe shown in Table 1.

According to the present invention, the gas displacement is performedafter the deaeration in the chamber, thus the air in the space and thecontent in the packaging container can be displaced by gas at a highrate of displacement in comparison with the gas flush type gasdisplacement method. Seal packaging requires no heat-shrinkable film,thus reducing the number of packaging materials to be used, andentrepreneur's bearing of cost based on the Container and PackageRecycling Law. Further, the overlapping ridges of the receptacle and thelid can be sealed with the band tape to enclose the packaging container,so that even if the shape or the size of the packaging containerschanges when performing packaging by using a device, a height of theband tape may be only adjusted to match a height of the overlappingridges of the receptacle and the lid. There is no need for selectingmaterials for the plastic package, and opening is extremely easy. TABLE1 Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example6 example 1 Multilayer film Layer Outermost PP NY NY NY NY PP configu-layer Thick- Coextrusion Coextrusion Coextrusion Coextrusion CoextrusionCoextrusion ration ness (μm)  7  5  5  5  5  7 Internal layer Adhesivelayer EVOH EVOH EVOH EVOH Adhesive layer Thickness (μm) CoextrusionCoextrusion Coextrusion Coextrusion Coextrusion Coextrusion  5  5  5  5 5  5 Internal layer EVOH NY NY NY NY EVOH Thickness (μm) CoextrusionCoextrusion Coextrusion Coextrusion Coextrusion Coextrusion  6  5  5  5 5  6 Internal layer Adhesive layer Adhesive layer Adhesive layerAdhesive layer Adhesive layer Adhesive layer Thickness (μm) CoextrusionCoextrusion Coextrusion Coextrusion Coextrusion Coextrusion  5  5  5  5 5  5 Internal layer PP PP PS LL EVA PP (laminate sur- CoextrusionCoextrusion Coextrusion Coextrusion Coextrusion Coextrusion face)Thickness  7  30  30  30  30  7 (μm) Thickness of multilayer film (μm) 30  50  50  50  50  30 Adhesive layer (dry laminate) Urethane UrethaneUrethane Urethane Urethane Urethane Thickness (μm)  5  5  5  5  5  5Resin sheet for container PP filler PP filler PP filler PP filler PPfiller PP filler PP filler Draw ratio Length to width Undrawn UndrawnUndrawn Undrawn Undrawn Undrawn Undrawn Thickness (μm) 450 450 450 450450 450 450 02TR ml/m³/D/MPa Less than 10 Less than 10 Less than 10 Lessthan 10 Less than 10 Less than 10 5000 or more Multilayer film LayerOutermost PP NY NY NY NY NY configu- layer Thick- CoextrusionCoextrusion Coextrusion Coextrusion Coextrusion Coextrusion ration ness(μm)  7  5  5  5  5  5 Internal layer Adhesive layer EVOH EVOH EVOH EVOHEVOH Thickness (μm) Coextrusion Coextrusion Coextrusion CoextrusionCoextrusion Coextrusion  5  5  5  5  5  5 Internal layer EVOH NY NY NYNY NY Thickness (μm) Coextrusion Coextrusion Coextrusion CoextrusionCoextrusion Coextrusion  6  5  5  5  5  5 Internal layer Adhesive layerAdhesive layer Adhesive layer Adhesive layer Adhesive layer Adhesivelayer Thickness (μm) Coextrusion Coextrusion Coextrusion CoextrusionCoextrusion Coextrusion  5  5  5  5  5  5 Internal layer PP PP PS LL EVAEVA (laminate sur- Coextrusion Coextrusion Coextrusion CoextrusionCoextrusion Coextrusion face) Thickness  7  30  30  30  30  30 (μm)Thickness of multilayer film (μm)  30  50  50  50  50  50 Adhesive layer(dry laminate) Urethane Urethane Urethane Urethane Urethane UrethaneThickness (μm)  5  5  5  5  5  5 Resin sheet for lid OPS OPS OPS OPS OPSOPS OPS Draw ratio Length to width 4 × 4 4 × 4 4 × 4 4 × 4 4 × 4 4 × 4 4× 4 Thickness (μm) 250 250 250 250 250 250 250 02TR ml/m³/D/MPa Lessthan 10 Less than 10 Less than 10 Less than 10 Less than 10 Less than 105000 or more Band tape Film NY NY PP/EVOH/PP PP/EVOH/PP PP/EVOH/PPPP/EVOH/PP NY Thickness (μm)  30  30  30  30  30  30  30 AdhesiveAcrylic Synthetic Acrylic Synthetic Acrylic Synthetic Acrylic Amount of 25 rubber  25 rubber  25 rubber  25 coating (g/m³)  25  25  25 Adhesivelabel Film PET PET PET PET PET PET PET Thickness (μm)  75  50  75  50 75  75  75 Adhesive Amount of Acrylic Acrylic Acrylic Acrylic AcrylicAcrylic Acrylic coating (g/m³)  25  25  25  25  25  25  25 Concentrationof Immediately G G G G G G G oxygen in after sealing package One daylater G G G G G G M Ten days later G G G G G G P General viableImmediately 1.1 × 10¹ 1.1 × 10¹ 1.1 × 10¹ 1.1 × 10¹ 1.1 × 10¹ 1.1 × 10¹1.1 × 10¹ cell count after One day later 4.4 × 10¹ 4.3 × 10¹ 7.4 × 10¹2.4 × 10¹ 3.4 × 10¹ 2.4 × 10¹ 6.4 × 10⁵ Three days 3.2 × 10² 2.2 × 10²3.8 × 10² 3.2 × 10² 3.5 × 10² 3.6 × 10² 2.2 × 10⁷ later Seven days 6.2 ×10¹ 6.1 × 10⁴ 5.9 × 10⁴ 4.5 × 10⁴ 5.3 × 10⁴ 5.2 × 10⁴ 8.3 × 10⁹ laterPP: Propylene resinNY: Nylon resinEVOH: Ethylene-vinyl acetate copolymer saponified resinLL: Linear polyethylene resinEVA: Ethylene-vinyl acetate copolymer resinAdhesive layer: Maleic acid modified polyolefin resinPS: Polystyrene resin

1. A method of manufacturing a gas displacement package characterized inthat a container comprises a receptacle and a lid, the receptacle andthe lid are overlapped each other at respective edge portions to cover atop of the receptacle, the overlapped portions are sealed with a bandtape, the container has a hole, air in the container is expelled throughthe hole and displaced by gas other than air, and then the hole issealingly closed.
 2. A method of manufacturing a gas displacementpackage as claimed in claim 1, characterized in that the container ismade of plastic.
 3. A method of manufacturing a gas displacement packageas claimed in claim 1 or 2, characterized in that the container, theband tape and an adhesive label have a gas barrier property.
 4. A methodof manufacturing a gas displacement package as claimed in claim 1 or 3,characterized in that the receptacle and the lid have at their edgeportions flanges including horizontal portions horizontally extendingfrom their openings, substantial vertical portions vertically extendingfrom ends of the horizontal portions, and ridges at boundaries betweenthe horizontal and vertical portions, and among the vertical portions ofthe flanges, the vertical portion located inside with respect to thecontainer is longer than the vertical portion located outside withrespect to the container, the inside vertical portion has a step at aportion in contact with an end of the outside vertical portion, and theband tape is adhered over the step for sealing.
 5. A method ofmanufacturing a gas displacement package as claimed in claim 1 or 3,characterized in that the hole for gas displacement is provided on a topsurface of the lid.
 6. A method of manufacturing a gas displacementpackage as claimed in claim 1 or 3, characterized in that the verticalportions of the flanges vertically extend downwardly from the horizontalportions.
 7. A packaging container characterized in that a receptacleand a lid have at their edge portions flanges including horizontalportions horizontally extending from their openings, and substantialvertical surfaces vertically extending from ends of the horizontalportions, and among the flanges, the vertical portion located insidewith respect to the container is longer than the vertical portionlocated outside with respect to the container, and the inside verticalportion has a step at a portion in contact with an end of the outsidevertical portion.
 8. A packaging container as claimed in claim 7,characterized in that a ridge of the lid and/or a ridge of thereceptacle has recesses formed in such a manner that the verticalportion is dented inwardly and the horizontal portion is denteddownwardly.
 9. A packaging container as claimed in claim 7 or 8,characterized in that the packaging container has a reinforcing surfacethat extends outwardly and horizontally from the end of the insidevertical portion.
 10. A package obtained by the method of manufacturinga gas displacement package according to any one of claims 1-6.